org.openimaj.util.hash

Class HashCodeUtil

java.lang.Object

org.openimaj.util.hash.HashCodeUtil

public final class HashCodeUtil
extends Object

Collected methods which allow easy implementation of hashCode. The following utility class allows simple construction of an effective hashCode method. It is based on the recommendations of Effective Java, by Joshua Bloch. Example use case:

  public int hashCode(){
    int result = HashCodeUtil.SEED;
    //collect the contributions of various fields
    result = HashCodeUtil.hash(result, fPrimitive);
    result = HashCodeUtil.hash(result, fObject);
    result = HashCodeUtil.hash(result, fArray);
    return result;
  }
 

Field Summary

Fields

Modifier and Type	Field and Description
static int	SEED An initial value for a hashCode, to which is added contributions from fields.

Constructor Summary

Constructors

Constructor and Description
HashCodeUtil()

Method Summary

Modifier and Type	Method and Description
static int	hash(int aSeed, boolean aBoolean) booleans.
static int	hash(int aSeed, boolean[] array) boolean array
static int	hash(int aSeed, char aChar) chars.
static int	hash(int aSeed, double aDouble) doubles.
static int	hash(int aSeed, float aFloat) floats.
static int	hash(int aSeed, int aInt) ints.
static int	hash(int aSeed, long aLong) longs.
static int	hash(int aSeed, Object aObject) aObject is a possibly-null object field, and possibly an array.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SEED

public static final int SEED

An initial value for a hashCode, to which is added contributions from fields. Using a non-zero value decreases collisions of hashCode values.

See Also:

Constant Field Values

Constructor Detail

HashCodeUtil

public HashCodeUtil()

Method Detail

hash

public static int hash(int aSeed,
                       boolean aBoolean)

booleans.

Parameters:

aSeed - the hash value to append to

aBoolean - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       char aChar)

chars.

Parameters:

aSeed - the hash value to append to

aChar - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       int aInt)

ints.

Parameters:

aSeed - the hash value to append to

aInt - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       long aLong)

longs.

Parameters:

aSeed - the hash value to append to

aLong - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       float aFloat)

floats.

Parameters:

aSeed - the hash value to append to

aFloat - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       double aDouble)

doubles.

Parameters:

aSeed - the hash value to append to

aDouble - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       Object aObject)

aObject is a possibly-null object field, and possibly an array. If aObject is an array, then each element may be a primitive or a possibly-null object.

Parameters:

aSeed - the hash value to append to

aObject - the value to hash

Returns:

the new hash value

hash

public static int hash(int aSeed,
                       boolean[] array)

boolean array

Parameters:

aSeed - the hash value to append to

array - the value to hash

Returns:

the new hash value